#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int missingNumber(int* nums, int numsSize) 
{
    int mid = numsSize;
    int ret = (0 + mid) * (mid + 1) / 2;
    for (int i = 0; i < numsSize; i++)
    {
        ret -= nums[i];
    }
    return ret;
}